| Water is the main limiting factor of the vegetation that growth in arid areas, so rainfall use efficiency of arid vegetation is very important. Haloxylon ammodendron and Haloxylon persicum are dominant species of Gurbantonggut desert, so study the water use mechanism of them is very important to predict the develop of population and give the scientific protect measurement in the climate change background. This paper in order to analysis how H. ammodendron and H. persicum use of rainfall, and rainfall use efficiency different of the two species by study rainfall redistribution, root distribution in less than 100cm depth and the water traits of the two species. The results showed that:(1) In 30mm/h rainfall intensity, stemflow, throughfall, interception of H. ammodendron and H. persicum are 7.3±0.47%,85.0±0.43%,7.7±0.71% and 6.7±0.23%,84.1±1.05%, 9.2±1.04%; in 20mm/h rainfall intensity, stemflow, throughfall, interception of H. ammodendron and H. persicum are 16.7±1.37%,77.8±0.78%,5.3±0.77% and 19.2±1.42%, 75.6±1.06%,5.2±0.79%. AVNOA shows that rainfall redistribution was no significant difference of H. ammodendron and H. persicum in the same rainfall intensity, but rainfall intensity can significantly affect their rainfall redistribution, respectively.(2) Regression analysis indicate that stemflow(mm) and throughfall(mm) of H. ammodendron and H. persicum are significant linear relationship and interception(mm) is a significant exponentially with rainfall depth. Stemflow rate, throughfall rate and interception rate are significant logarithmic relationship with rainfall depth.(3) Whether in each of the two simulate rainfall intensity, funneling ratio of H. persicum is large than it of H. ammodendron, In 30mm/h rainfall intensity, the average funneling ration of H. ammodendron and H. persicum are 34.1 and 43.1, respectively; in 30mm/h rainfall intensity, the average funneling ration of H. ammodendron and H. persicum are 70.6 and 100.2, respectively.(4) The lateral root of H, ammodendron and H. persicum mainly distribute in 0～60cm soil layer, they are occupied 96% and 86% of all lateral roots. The lateral roots of H. persicum are very abundance in 0-60cm soil layer, the average number of all lateral roots is 252.5, but in which diameter<lmm is 207.5. In contrast, lateral roots of H. ammodendron is very few the average number of all lateral roots is 25.25, but in which diameter<lmm is only 0.75. H. persicum lateral root average horizontal spread distance are 2.2 and 3.1times of H. ammodendron, with diameter of 1～5mm and >5mm.(5) H. ammodendron and H. persicum can absorb water by assimilation twig. When submerge in water for 10 minutes the assimilation twig water absorption are 5.3% and 4.0%; for 20 minutes, the water absorption are 9.8% and 7.4%. (6) The dry weight of air dry water loss experiment assimilation twig is larger than it of assimilation twig water absorb experiment of the two species. This indicates that the assimilation twig has loss nutrient when it is submerged in water, this also implies that stemflow and throughfall can concentrate nutrient from the assimilation twig.Summarize the study above can conclude that H. persicum use rainfall more efficiency by distribute more water to stemflow and cooperate with root distribution. H. ammodendron use rainfall very little, but prefer to use ground water. |
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